Definitions

# Metre per second

Metre per second (U.S. spelling: meter per second) is an SI derived unit of both speed (scalar) and velocity (vector quantity which specifies both magnitude and a specific direction), defined by distance in metres divided by time in seconds.

The official SI symbolic abbreviation is m·s−1, or equivalently, m/s; although the abbreviation mps is sometimes used colloquially, but is incorrect according to the BIPM. Where metres per second are several orders of magnitude too slow to be convenient, such as in astronomical measurements, velocities may be given in terms of kilometres per second, where 1 km/s is equivalent to 1,000 metres per second; in popular, non-science literature kps is occasionally, and again incorrectly, used instead of km/s.

One metre per second is roughly the speed of an average person walking.

## Conversions

1 metre per second is equivalent to:
= 3.6 km·h−1 (exactly)
≈ 3.2808 feet per second (approximately)
≈ 2.2369 miles per hour (approximately)

foot per second = 0.3048 m·s−1 (exactly)

mile per hour ≈ 0.4471 m·s−1 (approximately)

km·h-1 ≈ 0.2778 m·s−1 (approximately)

1 kilometre per second is equivalent to:

≈ 0.6213 miles per second (approximately)
≈ 2237 miles per hour (approximate)

## Relation to other measures

Although m·s−1 is an SI derived unit, it could be viewed as more fundamental than the metre, since the latter is derived from the speed of light in a vacuum, which is defined as exactly 299 792 458 m·s−1 by the BIPM. It follows that one metre is the length of the path travelled by light in a vacuum during a time interval of 1/299 792 458 of one second.